UNCONVENTIONAL BOREHOLE BREAKOUT ROTATION ANALYSIS PROVIDES A QC TOOL FOR STRESS MODELS

2006 ◽  
Vol 46 (1) ◽  
pp. 307
Author(s):  
B.A. Camac ◽  
S.P. Hunt ◽  
P.J. Boult ◽  
M. Dillon
Keyword(s):  
Principal Stress ◽  
Input Data ◽  
Distinct Element ◽  
Maximum Principal Stress ◽  
Principal Stresses ◽  
Stress Regime ◽  
Seal Integrity ◽  
Borehole Breakout ◽  
Stress Models ◽  
Kupe Field

In distinct element (DEM) numerical stress modelling, the principal stress magnitudes and orientations are applied to the boundary of the 3D model. Due to data restrictions and typical depths of investigation, it is possible to have much uncertainty in the conventional methodologies used to constrain the regional principal stress magnitudes and orientations.A case study from the Kupe field in the Taranaki Basin, New Zealand is presented where the uncertainty in the input data made it difficult to determine which stress regime—a transitional normal/strike-slip or reverse/thrust—is active at reservoir depth (approximately 3,000 m). The magnitudes and orientation of the principal stresses were constrained using published techniques. A sensitivity analysis was applied to account for the uncertainty in the input data. A model of the Kupe field incorporating 18 major faults was subsequently loaded under both derived stressed regimes, using the calculated magnitudes.Borehole breakout analysis was used to acquire interpreted orientations of the maximum principal stress (Shmax). The work presented herein describes a different or unconventional approach to the general petroleum geomechanics methodology. Typically, the breakout data is averaged to get one data point per well location. Here, all breakout data is retained and displayed vertically. The data is actively used and the variations with depth can be seen to show how faults can generate local perturbations of the regional stress trajectory. These data are then used to compare the observed or field indications of the breakouts along the borehole with the modelled Shmax predicted by both end point DEM stress models. This comparison has provided additional confidence in the derived stress regime and the derived stress models for the Kupe field. The stress models are used to predict areas of enhanced hydrocarbon pooling and low seal integrity.

Characteristics of in situ stress field in the Huainan mining area, China and its control factors

2021 ◽  
Author(s):  
Xiuchang Shi ◽  
Jixing Zhang ◽  
Guoqing Li
Keyword(s):  
Principal Stress ◽  
Mining Area ◽  
Maximum Principal Stress ◽  
Geological Structure ◽  
In Situ Stress ◽  
Burial Depth ◽  
Principal Stresses ◽  
Support Design ◽  
Control Factors

Abstract Due to the high in situ stresses, dynamic disasters occurred frequently in the Huainan mining area, China. While our understanding of the in situ stresses in this area is still insufficient. In this study, the in situ stresses of 18 sections in two boreholes in the Xinji No. 1 coalfield were measured by using hydraulic fracturing method, and the distribution of in situ stresses in the Huainan mining area were investigated. The relationship between in situ stress and geological structure in the Huainan mining area were summarized and the limitation of fault friction strength on in situ stresses were discussed. The result showed that the maximum horizontal principal stress (σH) at Xinji No. 1 mine was 13.95–25.23 MPa, the minimum horizontal principal stress (σh) was 12.16–21.17 MPa. The average azimuth of the maximum horizontal principal stress was N83.61 °E. The statistical results showed that the in situ stresses in Huainan mining area were characterized by a strike-slip faulting regime. Both the horizontal and vertical principal stresses increased approximately linearly with the increase of burial depth. The direction of the maximum principal stress in the study area is closely related to the tectonic movement and the ratio of maximum principal stress to minimum principal stress was primarily limited by the friction strength of fault. The outcomes of this research can provide some reliable engineering parameters and benefit the roadway layout and support design in the Huainan mining area.

FAULT AND TOP SEAL INTEGRITY AT RELAYS AND INTERSECTIONS USING A 3D DISTINCT ELEMENT CODE

2004 ◽  
Vol 44 (1) ◽  
pp. 481 ◽  
Author(s):  
B.A. Camac ◽  
S.P. Hunt ◽  
P.J. Boult
Keyword(s):  
Rock Mass ◽  
Principal Stress ◽  
Fault Plane ◽  
Numerical Technique ◽  
Distinct Element ◽  
South Australia ◽  
Local Stress ◽  
Surrounding Rock ◽  
Regional Stress ◽  
Seal Integrity

It has long been known that faults and horizon boundaries can greatly affect the magnitude and orientation of the in-situ rock stress state. Significant success has been shown in the geo-engineering disciplines, whereby geomechanical models have been built to model local stress fields generated by rock mass inhomogeneities.In this work 3DEC (3D) the discrete element code has been applied to model stress perturbations around three simple fault configurations, two relay configurations (relay ramp and horst structure) and one fault intersection. The results show rotation in the principal stress orientation and stress magnitudes of the regional stress field about the faults. The degree of rotation of the principal stress direction and the stress magnitude are dependant on the fault friction angle parameter, the angle of maximum principal stress to the fault plane and the ratio of maximum to minimum principal stress. The degree of perturbation is demonstrated graphically in the surrounding rock mass along the fault strike, the perturbation generated by the fault can be up to 1.4 times the magnitude of the maximum principal regional stress and is highly dependent on friction angle.Case studies are presented where this 3D numerical technique has been used to truly integrate risking methods on the fault plane and in the surrounding rock mass. Case study examples are given for the Otway Basin, South Australia and the Bonaparte Basin, Timor Sea, where these predictors can be applied to accurately identify high-risk reservoir seals.

scholarly journals How many implants are needed for mandibular full-arch rehabilitation?

2020 ◽  
Vol 19 ◽  
pp. e209191
Author(s):  
Karina Giovanetti ◽  
Ricardo Armini Caldas ◽  
Paulo Henrique Ferreira Caria
Keyword(s):  
Bone Tissue ◽  
Principal Stress ◽  
Three Dimensional ◽  
Maximum Principal Stress ◽  
Von Mises Stress ◽  
Principal Stresses ◽  
Dimensional Finite Element ◽  
The Difference ◽  
Von Mises ◽  
Three Dimensional Finite Element

Aim: To analyze the stress distribution at the peri-implant bone tissue of mandible in full-arch implant-supported rehabilitation using a different number of implants as support. Methods: Three-dimensional finite element models of full-arch prosthesis with 3, 4 and 5 implants and those respective mandibular bone, screws and structure were built. ANSYS Workbench software was used to analyze the maximum and minimum principal stresses (quantitative analysis) and modified von Mises stress (qualitative analysis) in peri-implant bone tissue after vertical and oblique forces (100N) applied to the structure at the cantilever site (region of the first molars). Results: The peak of tensile stress values were at the bone tissue around to the distal implant in all models. The model with 3 implants presented the maximum principal stress, in the surrounding bone tissue, higher (~14%) than the other models. The difference of maximum principal stress for model with 4 and 5 implants was not relevant (~1%). The first medial implant of the model with 5 implants presented the lower (17%) stress values in bone than model with 3 implants. It was also not different from model with 4 implants. Conclusion: Three regular implants might present a slight higher chance of failure than rehabilitations with four or five implants. The use of four implants showed to be an adequate alternative to the use of classical five implants.

Frequency Distribution Curves for Main Steam Piping Multiaxial Stresses

2014 ◽  
Author(s):  
Marvin J. Cohn ◽  
Fatma G. Faham ◽  
Dipak Patel
Keyword(s):  
Principal Stress ◽  
Frequency Distribution ◽  
Creep Damage ◽  
Maximum Principal Stress ◽  
Piping System ◽  
Principal Stresses ◽  
Piping Systems ◽  
Girth Welds ◽  
Main Steam ◽  
Hoop Stresses

A high energy piping (HEP) asset integrity management program is important for the safety of plant personnel and reliability of the generating unit. HEP weldment failures have resulted in serious injuries, fatalities, extensive damage of components, and significant lost generation. The main steam (MS) piping system is one of the most critical HEP systems. Creep damage assessment in MS piping systems should include the evaluation of multiaxial stresses associated with field conditions and significant anomalies, such as malfunctioning supports and significant displacement interferences. This paper presents empirical data illustrating that lead-the-fleet girth welds of MS piping systems have creep failures which can be successfully ranked by a multiaxial stress parameter, such as maximum principal stress. Both the as-found elastic (initial) stress and inelastic (redistributed) stress at the piping outside diameter surface are evaluated for the base metal of three MS piping systems. Frequency distribution curves are then developed for the initial and redistributed piping stresses. The frequency distribution curves are subsequently included on a Larson Miller Parameter (LMP) plot for the applicable material, revealing the few critical (lead-the-fleet) girth welds selected for nondestructive examination (NDE). By including an evaluation of significant field anomalies, multiaxial operating stress on the outside surface, and weldment performance, it is shown that there is a good correlation of calculated creep stress versus the operating time of observed creep damage. This process also reveals the large number of MS piping girth welds that have insufficient applied stress to have substantial creep damage within the expected unit life time (assuming no major fabrication defects). API 579 recommends an effective stress to compute the creep rupture life using the LMP. This constitutive stress equation includes a combination of the maximum principal, von Mises, and hydrostatic stresses. Considering the stresses in these three MS piping systems, this paper reveals that when the axial and hoop stresses are nearly the same values, the API 579 effective stress may be 10% greater than the maximum principal stress. However, the maximum principal stresses are greater than the API 579 effective stresses at the maximum stress locations in the three MS piping systems, because the axial stresses are significantly greater than the hoop stresses. This study also provides a comparison of the results of a conventional American Society of Mechanical Engineers (ASME) B31.1 Code as-designed sustained stress analysis versus the redistributed maximum principal stresses for a complete set of MS piping system nodes. A comparison of Code-sustained load versus redistributed maximum principal stress results are illustrated on frequency distribution curves.

Vein geometry and hydrostatics during Yellowknife mineralisation

1978 ◽  
Vol 15 (10) ◽  
pp. 1653-1660 ◽  
Author(s):  
R. Kerrich ◽  
I. Allison
Keyword(s):  
Principal Stress ◽  
Shear Zone ◽  
Fluid Pressure ◽  
Shear Zones ◽  
Horizontal Stress ◽  
Maximum Principal Stress ◽  
Ambient Conditions ◽  
Stress Regime ◽  
Quartz Veins ◽  
Vertical Arrays

Three vein systems with distinct geometry and time relations are located within major ductile shear zones at Yellowknife. En échelon arrays of centimetre width quartz veins initiated at ~45° to the shear zone boundaries and normal to the schistosity during initial translation on the structures. These geometrical relations conform to the simple shear model of Ramsay and Graham. Orientation of the maximum principal stress was ~45° to the 70° dipping shear zone boundaries, implying that the horizontal stress in the crust was greater than the vertical stress.Gold-bearing quartz veins of metre dimensions are disposed parallel to the schistosity, cross cutting early veins. This geometry requires the stress regime to switch from the former orientation such that the maximum principal stress is parallel to the schistosity, and the effective stress normal to the schistosity is tensile. The change of stress orientation is attributed to transient high fluid pressure which generated hydraulic fracturing and correspondingly high values of permeability. Under these conditions the shear zones act as conduits for massive fluid discharge; quartz and gold were precipitated from solutions cooling along a temperature–pressure (TP) gradient. Crustal vertical stress was greater than horizontal stress.Late stage lenticular gold-bearing quartz veins of metre dimensions were emplaced as vertical arrays within the shear zones, oriented normal to schistosity. These tension fractures formed when the stress regime reverted to the ambient conditions for stage 1 veining during a second episode of displacement on the shear zones. Consideration of the kinetics of intergranular diffusion, with reference to the required transport distances of gold into a lode deposit, implies that long-range diffusive transport of gold into veins was not significant.

scholarly journals Finite Element Analysis of Traditional and New Fixation Techniques of the 3D-Printed Composite Interlocking Nail in Canine Femoral Shaft Fractures

2020 ◽  
Vol 10 (10) ◽  
pp. 3424
Author(s):  
Siwasit Pitjamit ◽  
Wasawat Nakkiew ◽  
Kriangkrai Thongkorn ◽  
Warinthorn Thanakulwattana ◽  
Kittiya Thunsiri
Keyword(s):  
Principal Stress ◽  
Femoral Shaft ◽  
Shaft Fracture ◽  
Maximum Principal Stress ◽  
Fixation Technique ◽  
Principal Stresses ◽  
Interlocking Nail ◽  
Locking Screws ◽  
Fixation Techniques ◽  
3D Printed

Since the removal of a metallic interlocking nail system leaves a blank cavity inside a healed bone, bioactive and biodegradation materials have been used instead to induce bone formation and eliminate complications of the material removal procedure. The previous study presented the possibility of an interlocking nail fabrication from polylactic acid (PLA), polycaprolactone (PCL), and hydroxyapatite (HA) using 3D printing, namely fused filament fabrication (FFF), for canine diaphyseal fractures. Therefore, a finite element analysis (FEA) was used to predict the maximum principal stress of this 3D-printed composite interlocking nail to stabilize a canine femoral fracture, and the biomechanical performance was evaluated for the treatment of canine femoral shaft fractures using both traditional and new fixation techniques. Three-dimensional FEA models were created, and the composite interlocking nail was tested for implant strength and stability. Three types of canine femoral shaft fracture (proximal shaft fracture, middle shaft fracture, and distal shaft fracture) fixed by traditional and new fixation techniques, consisting of two, four, and six locking screws, were analyzed with a multilevel factorial design technique. The maximum principal stresses of the composite interlocking nail were compared with each fixation technique. According to the multilevel factorial design, gap type, fracture gap, and fixation techniques are factors that affect the maximum principal stress of the composite interlocking nail for two and four locking screws. For six locking screws, all factors, including gap type, fracture gap, nail length, and fixation techniques, significantly affect the maximum principal stress. The use of a 3D-printed composite interlocking nail system with new fixation techniques demonstrated lower maximum principal stresses than the interlocking nail system that used a traditional fixation technique. The results of this study could help orthopedic veterinary surgeons to understand the biomechanical performances of traditional and new fixation techniques. Furthermore, surgeons may use the numerical results of this analysis to choose a fixation technique based on a patient’s condition.

State of Stress in Azeri-Chirag-Gunashli Anticline Structure, South Caspian Sea

2021 ◽  
Author(s):  
Reza Majidi ◽  
Abbas Abbasov ◽  
Elshan M. Aliyev ◽  
Firangiz Akhundova ◽  
Joanna Mckidd
Keyword(s):  
Principal Stress ◽  
Image Data ◽  
Active Regions ◽  
Relative Magnitude ◽  
Maximum Principal Stress ◽  
South Caspian Basin ◽  
Principal Stresses ◽  
Ratio Distribution ◽  
Distribution Maps ◽  
Integrity Tests

Abstract The Azeri-Chirag-Gunashli (ACG) field, a tightly folded anticline structure, located offshore Azerbaijan in the south Caspian basin, is one of the most tectonically active regions of the world. Understanding the stress state across the ACG structure is a key to successful development of the field by optimizing well placement during drilling, completion, and depletion/injection phases. This article summarizes the results of studies undertaken on the state of the stress in ACG field. It encompasses the field-wide overview of stresses from a structural standpoint, the compilation of drilling and completion events, for instance, induced fracture during lost circulation events, and Formation Pressure Integrity Tests (FPIT) as well as analysis of wellbore breakout from variety of sources including borehole image data and caliper logs that were used to infer the magnitude and orientation of far-field stresses. Key outcomes of this study are the stress ratio distribution maps and stress orientation maps across the structure, based on the magnitude and orientations of stresses that were inferred from drilling events and wellbore breakouts. Results of this analysis show that magnitude and orientation of stresses vary across the structure both laterally and vertically. Minimum principal stress (Shmin) tends to increase from the crest toward the flanks. The maximum principal stress (SHmax) orientation is found to be predominantly sub-perpendicular to the strike of the anticline structure (60°-80° N), influenced by the reginal tectonic stresses. Moreover, stress rotation from sub-perpendicular to sub-parallel to the anticline is observed over some parts of the central and crestal areas, indicating that stresses are less compressional at the center and crest of the Azeri anticline. Local variability is possibly due to proximity to geological features such as mud volcanos, faults, and high deformation areas. The relative magnitude of stresses found in ACG, suggests a predominantly strike-slip faulting regime (where SHmax is the greatest of the three principal stresses) particularly, at the flanks and noses of the structure.

scholarly journals Elastic Simulation of Joints with Particle-Based Fluid

2021 ◽  
Vol 11 (15) ◽  
pp. 6900
Author(s):  
Su-Kyung Sung ◽  
Sang-Won Han ◽  
Byeong-Seok Shin
Keyword(s):  
Principal Stress ◽  
Human Body ◽  
Yield Condition ◽  
Maximum Principal Stress ◽  
Human Motion ◽  
The Difference ◽  
The Moment ◽  
External Forces ◽  
Physical Changes ◽  
Elastic Simulation

Skinning, which is used in skeletal simulations to express the human body, has been weighted between bones to enable muscle-like motions. Weighting is not a form of calculating the pressure and density of muscle fibers in the human body. Therefore, it is not possible to express physical changes when external forces are applied. To express a similar behavior, an animator arbitrarily customizes the weight values. In this study, we apply the kernel and pressure-dependent density variations used in particle-based fluid simulations to skinning simulations. As a result, surface tension and elasticity between particles are applied to muscles, indicating realistic human motion. We also propose a tension yield condition that reflects Tresca’s yield condition, which can be easily approximated using the difference between the maximum and minimum values of the principal stress to simulate the tension limit of the muscle fiber. The density received by particles in the kernel is assumed to be the principal stress. The difference is calculated by approximating the moment of greatest force to the maximum principal stress and the moment of least force to the minimum principal stress. When the density of a particle increases beyond the yield condition, the object is no longer subjected to force. As a result, one can express realistic muscles.

FEM Stress Analysis and Strength of Scarf Adhesive Joints of Similar Adherend Subjected to Impact Tensile Loadings

2007 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Yuya Hirayama ◽  
He Dan
Keyword(s):  
Young’S Modulus ◽  
Principal Stress ◽  
Stress Wave ◽  
Young's Modulus ◽  
Three Dimensional ◽  
Maximum Principal Stress ◽  
Adhesive Joints ◽  
Stress Wave Propagation ◽  
Adhesive Thickness ◽  
Three Dimensional Finite Element

The stress wave propagation and stress distribution in scarf adhesive joints have been analyzed using three-dimensional finite element method (FEM). The FEM code employed was LS-DYNA. An impact tensile loading was applied to the joint by dropping a weight. The effect of the scarf angle, Young’s modulus of the adhesive and adhesive thickness on the stress wave propagations and stress distributions at the interfaces have been examined. As the results, it was found that the point where the maximum principal stress becomes maximum changes between 52 degree and 60 degree under impact tensile loadings. The maximum value of the maximum principal stress increases as scarf angle decreases, Young’s modulus of the adhesive increases and adhesive thickness increases. In addition, Experiments to measure the strains and joint strengths were compared with the calculated results. The calculated results were in fairly good agreements with the experimental results.

Influence of Slope Gradient on Distribution Rule of Geostress Field in River Valleys

2013 ◽  
Vol 404 ◽  
pp. 365-370 ◽  
Author(s):  
Qi Tao Pei ◽  
Hai Bo Li ◽  
Ya Qun Liu ◽  
Jun Gang Jiang
Keyword(s):  
Numerical Simulation ◽  
Stress Concentration ◽  
Principal Stress ◽  
Three Dimensional ◽  
Maximum Principal Stress ◽  
Slope Gradient ◽  
Bank Slope ◽  
Distribution Rule ◽  
River Valleys ◽  
Gradient Change

During the construction of hydropower station, the change of slope gradient in river valleys often takes place. In order to study influence of slope gradient change on distribution rule of geostress field, the three dimensional unloading models under different slope gradients were established by finite difference software (FLAC3D). After numerical simulation, the results were as follows: (1) The phenomenon of stress concentration at the bottom of river valleys was obvious, which appeared the typical stress fold. Both the depth of stress concentration zone and the principal stress values significantly increased with the increment of slope gradient. (2) Maximum principal stress values increased less in shallow part of upper bank slope (low stress zone) but increased more in the nearby slope foot with the increment of slope gradient, causing great difference in geostress field of bank slope. (3) There was some difference in released energy of bank slope due to slope gradient change in river valleys. In order to distinguish the difference, stress relief zone was further divided into stress stably released zone and stress instability released zone. Finally, take Ada dam area of the western route project of South-to-North Water Transfer as an example, the results by numerical simulation were reliable through comparing the distribution rule of geostress field for the dam, which could provide important reference for stability of the design and construction of steep and narrow river valleys.

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